Electric circuit breaker



Nov. 26, 1940. w. K. RANKIN ELECTRIC CIRCUIT BREAKER Filed June 22, 1939 Inventor William K. Rankin, b 1 2 His ttor-ney.

Patented Nov. 26, 1940 PATENT OFFICE 2,222,722 ELECTRIC CIRCUIT BREAKER William K. Rankin, Lansdowne, Pa., assignor to General Electric Company, a. corporation of New York Application June 22, 1939, Serial No. 280,535

3 Claims. ((71. 200-448) The present invention relates to electric circuit breakers, and particularly circuit breakers of the fluid blast type wherein one of the contact members forms a nozzle through which arc-ex- 5 tinguishing fluid is discharged during a circuitinterrupting operation of the switch.

In circuit breakers of the above type the contact area required for carrying the normal load current of the breaker necessitates the use of a 10 contact rod and nozzle of greater size than is necessary or desirable for efficientinterruption of [the circuit, even under short circuit conditions. For this reason, it is desirable to provide a nozzle of relatively small cross-sectional area so that 15 the arc-extinguishing fluid may be forced through the are at high velocity without the use of excessive quantities of fiuid and, at the same time, to provide a large contact area between the relatively movable contacts. Accordingly, it is a 20 primary object of the invention to provide a novel construction and arrangement in the relatively movable contacts of a fluid blast electric circuit breaker which reduces the fiuid requirement for effective operation and provides for a 25 large contact area between the relatively movable contacts of the circuit breaker.

It is another object of. the invention to provide an improved circuit breaker construction in which the current-carrying contacts are not sub- 30 jected to the arc or hot gases and thereby pitted or spattered with the hot metal particles which 1 are carried by the arc stream.

Further objects and advantages of the invention will become apparent as the following de- 35 scription proceeds, reference being had to the accompanying drawing in which Fig. 1 is an elevational view in section of a circuit breaker illustrating an embodiment of the present invention, and Fig; 2 is a sectional view taken along 40 the line 22 of Fig. 1.

Referring to the drawing the circuit breaker illustrated comprises a cylindrical housing it) of suitable insulating material which is closed at its opposite ends to form a pressure chamber. A

45 conduit l-I communicating with the interior of the housing I is connected to a suitable supply of arc-extinguishing fluid under pressure which may be, for example, compressed air. Arrangements for supplying air under pressure to switches of this character are well known, and, for purposes of simplifying the drawing, none is shown. The'upper end of the housing I0 is closed by'a fixed contact member I2 which in the form illustrated comprises a disk of con- 55 ducting material whici is secured within the upper end of the housing in any suitable manner. The stationary Contact is provided with a cylindrical depending portion l3 which extends into the arc chamber. An opening of circular crosssection is formed in the fixed contact and ex- 5 tends through both the disk'and the depending portions to form a nozzle communicating with the interior of the pressure chamber. Secured in the lower end of the housing I0 is a circular channel member M of L-shaped cross-section which is closed at its lower end by an annular plate or washer l5 to form a retainer for a spring pressed segmental contact ring l6 arranged to slidably engage a contact rod H which forms a movable contact element of the circuit breaker.

The end of the contact rod which engages the fixed contact ii. in the closed circuit position of the circuit breaker is specially constructed to cooperate with the fixed contact described above to provide a large contact area and control the flow of arc-extinguishing fluid through the opening in the fixed contact. In accordance with the present invention the end of the movable contact rod is constructed with a centrally located cylindrical contact portion N3 of small diameter in comparison with the size of the rod. This contact portion is received in the opening in the fixed contact in the closed circuit position of the breaker and acts to control the flow of arc-extinguishing fluid therethrough. Surrounding the contact portion l8 and, in the particular construction illustrated, concentrically therewith is an annular contact portion l9 arranged to engage the outer surface of the cylindrical depending portion 13 of the fixed contact. The contact i9 is formed by slotting the outer wall of the rod at spaced intervals to provide segmental contact portions which are spring pressed by a pair of helical springs 20. The fixed and movable contacts of the circuit breaker are connected to the circuit to be controlled by suitable conducting straps 2i and 22 which are electrically connected to the fixed contact I2 and the closure plate l5 of the contact l6 respectively. In the closed circuit position of the breaker illustrated in Fig. 1, it is apparent that a circuit is completed from the strap 2| through'fixed contact l2, parallel contact portions l8 and IQ of the movable contact rod, the body of the movable contact rod, the sliding contact l6, and the retainer ports i4 and [5 to the conducting strap 22. I

In operation of the breaker described above, the movable contact is moved away from the fixed contact by a suitable operating mechanism (not shown) in accordance with the circuit condition to be controlled. Simultaneusly, with the opening operation of the movable contact rod or in timed relation thereto arc-extinguishing fluid under pressure is supplied to the pressure chamber through the conduit II. As the movable contact is withdrawn the contact portion I8 first leaves the outer surface of the depending portion l3 and then the central contact portion II is withdrawn from the opening in the fixed contact and an arc is drawn between the walls surrounding the opening and the end of the contact portion I'll. At the instant of contact separation a fluid blast is directed through the arc and into the opening in the fixed contact to the surrounding atmosphere. Since the nozzle of the present construction is small compared with the current-carrying capacity of the breaker, the arcextinguishing fluid may be directed through the nozzle at high velocity without using excessive quantities thereof. Since the supply of arc-extinguishing fluid is an important problem and often a limitation in breaker installations of this type, the conservation of such fluid is a matter of considerable importance. From the preceding description of the operation of the circuit breaker embodying the invention, it is apparent that the are, which is drawn between the rod l8 and the end of the depending portion ll of the fixed contact, is blown away from the maincurrentcarrying portion I! of the movable contact and the cooperating outside surface ofthe portion l3 of the fixed contact, so that these surfaces are not subjected to the destructive action of the hot gases of the arc stream. This arrangement insures long life of the contacts and lower contact resistance.

While I have shown and described a particu-' lar embodiment of my invention, modifications thereof will be apparent to those skilled in the art. I do not, therefore, desire my invention to be limited to the particular construction shown and described, and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric circuit breaker of the fluid blast type comprising a pressure chamber, rela tively movable contacts separable in said chamber to form an arc therein, means for supplying an arc-extinguishing fluid under pressure to said chamber, one of said contacts including a cylindrical portion extending into said chamber and having an opening therein, the wall of said opening and the outer wall of said cylindrical portion forming inner and outer contact surfaces, the other oi said contacts having concentrically arranged contact portions engaging the inner and outer surfaces of said one contact in the closed circuit position of said breaker, the contact portion of said other contact engaging the inner contact surface of said one contact being constructed and arranged to control the flow of arc-extinguishing fluid through said opening and to engage said inner contact surface until after the other contact portions of said contacts have been separated during opening movement of said breaker so that the arc is drawn between said one contact and the portion of said other contact which controls the flow of arc-extinguishing fluid.

2. An electric circuit breaker of the fluid blast type comprising a pressure chamber, a fixed contact and a movable contact separable in said chamber to form an arc therein, and means for supplying an arc-extinguishing fluid under pressure to said chamber, said fixed contact having a portion thereof extending inwardly into said chamber and provided with an opening forming a blast nozzle, said movable contact having a current-carrying portion received in said opening in the closed circuit position of said breaker and another current-carrying portion engaging an outer surface of said inwardly extending portion, the portion of said movable contact received in said opening being constructed and arranged to control the flow of fluid through said opening and to engage said fixed contact until after the other current-carrying portion of said movable contact has separated from the fixed contact whereby an arc is drawn between the flxed contact and the portion of said movable contact which controls the flow of arcextinguishing fluid.

3. An electric circuit breaker of the fluid blast type comprising a pressure chamber, a fixed contact and a movable contact separable in said chamber to form an arc therein, and means for supplying an arc+extinguishing fluid under pressure to said chamber, said fixed contact having a cylindrical portion extending inwardly into said chamber and provided with an aperture forming a blast nozzle, said movable-contact having an annular contact portion arranged to engage the outer surface of the cylindrical in- WILLIAM K. RANmN. 

